Short Message Service (SMS) has been used in mobile communications networks to enable different subscribers to send short text messages to each other. The Mobile Subscriber ISDN Number (MSISDN), i.e. the phone number of the mobile subscriber is utilised as the identifying addressing information, since the SMS content is intended for a particular user. The SMS message and the MSISDN are provided to a SMS controller, which temporary stores the SMS and searches for the intended terminating mobile subscriber. In searching for the terminating mobile subscriber, the SMS controller interacts with a Home Location Register (HLR) for achieving identity data, International Mobile Subscriber Identity (IMSI), of a Subscriber Identity Module (SIM) associated with the terminating mobile subscriber. The HLR also provides an address of a Mobile Switching Centre (MSC) through which the SIM can be reached. By using this data, the message can be routed to the appropriate terminating mobile subscriber.
The SMS concept is today also used for several network-based applications, in which SMS is used to push data directly to a client in the phone. Examples of this are Over-The-Air (OTA) SMS, Multimedia Message Service (MMS) notifications and SIM Toolkit updates. In order to fit into the basic SMS concept, also those applications are using MSISDN as the address for reaching either the SIM card or the mobile terminal.
As long as there is a one-to-one correspondence between the MSISDN, the IMSI and the identity of the mobile terminal, e.g. defined by the International Mobile Equipment Identity (IMEI) or the IMEI extended with the software version (IMEISV), either of these quantities can be used for addressing purposes, giving the same terminating terminal, SIM and subscriber. However, by introducing more flexible solutions allowing e.g. a subscriber to move the SIM card between different terminals, or allowing a single mobile subscriber to have more than one SIM card addressed with the same MSISDN, addressing problems may arise.
A part of the work within 3GPP is directed to standardise a function to automatically detect when a SIM card identified by IMSI is used in a terminal identified by IMEISV for the first time. This function is named Automatically Device Detection (ADD). The information comprising at least MSISDN, IMSI and IMEISV is stored in a terminal capability server. The terminal capability server also has the capability to forward the relevant information to external applications, such as Device Management Systems (DMS). Those applications can use part of the information as triggers to different events. Examples are that SMS with new GPRS settings can be sent out to terminals that require those settings before they can be used for MMS, Wireless Application Protocol (WAP) or other data services. The terminal capability server thereby allows connected applications to solve the problems of moving the SIM card to different terminals. However, the problems remain for applications not connected to any updated terminal database and for the use of dual SIM cards.